This invention relates to library services and digital rights management. Reference, or context-sensitive, linking provides the ability to transmit bibliographic data through hypertext links and thereby to connect users who are searching in one reference collection with content in another collection. Such reference collections can include academic research journals, general interest magazines, e-books, bibliographic indexes, and other reference works and additional sources and services associated with the latter items. For example, a reference link can allow a user to move from an abstract of a document located in a collection from one publisher to the full-text content in another vendor database. Another link could allow a user to move from a bibliography in one document to a library catalog of related documents. Other links can allow users to move from one database to another, from a journal article to a web site and from an abstract to an on-line store where a full-text copy of the document can be purchased.
Initially, reference links were simple hyperlinks which were inserted into search result lists by the owner of the reference collection and typically point to predetermined resource copies. As useful as these hyperlinks were, they quickly generated a problem called the “appropriate-copy” problem. This problem occurs when a user locates a link to a resource that has multiple copies available, some of which the user can access via different routes that are governed by distinct access policies and associated with a distinct costs. For example, a simple link may point to a resource copy to which the user does not have access, but the user may have access to another copy of that resource via another route. Alternatively, the user may have access to several copies of the resource via routes that have different costs and, of course, the user would like to obtain the copy at the lowest cost. Thus, in order to be of most use to the user, a link to this resource should point to the resource copy that is most appropriate to that user and the circumstances surrounding user and the link (called the “context”).
In order to solve the appropriate copy problem, dynamic links are typically inserted into the collection by the owner. However, rather than pointing to a predetermined resource, each link is dynamic in the sense that the destination is determined or “resolved” at the time that link is accessed based on the user and the context. One method of implementing dynamic link resolution is to use a “link resolver”, which is a server managed by the collection owner. Because a collection owner, such as a library, has information regarding the collection, policies, and users, an owner-managed link resolver can provide the desired context-sensitive linking.
A typical owner-managed link resolver system 100 is shown in FIG. 1. In this system, a user searching in a collection via a conventional mechanism such as a browser receives, on the browser screen display 102, a search results list 104 containing links associated with resources, such as journals, in response to a query. In FIG. 1 resource links 106, 108 and 100 are shown. In a collection that operates with a link resolver, the search results list is modified to display a separate link resolver link associated with each resource link. For example, link resolver link 112 is associated with resource link 110. The link resolver link 112 contains a URL at which a link resolver server 116 is located and information identifying the resource. Selecting the link resolver link 112, sends this information to the link resolver server 116 as indicated schematically by arrow 114.
Generally, for a given resource, the URL information that is sent to server 116 is constructed according to a predetermined standard. One standard for formatting the URL information that is sent to the server 116 is called “OpenURL.” An OpenURL consists of a base URL, which points to the link resolver 116, and a “query” string, which contains bibliographic data identifying the resource, typically in the form of key-value pairs. The OpenURL standard is described in detail in the PDF document Z39—88—2004.pdf available from the National Information Standards Organization, 4733 Bethesda Avenue, Suite 300, Bethesda, Md. 20814. An example of a URL constructed in accordance with the current OpenURL standard is (the conventional http:// preface has been omitted to deactivate the link):
resolver.example.edu/cgi?url_ver=Z39.88-2004                &rft_val_fmt=info:ofi/fmt:kev:mtx:book        &rft.isbn=0836218310        &rft.btitle=Sample+Book+Title        
In this URL, the initial portion: “resolver.example.edu” is the URL of the link resolver server, for example, server 116. The suffix portion contains version information concerning the URL and resource identification information. In this case, the resource identification information includes the information type (book), the ISBN number of the book and its title.
A resource copy designed to be used with the OpenURL standard will contain only the suffix of the OpenURL query, leaving the URL of the link resolver server blank as follows:                ——————?genre=book&isbn=0836218310&title=Sample+Book+Title        
Any resource collection containing that resource will dynamically construct a URL in response to the selection of a link resolver link and preface the query portion of the URL with the URL of its particular link resolver server.
The link resolver 116 parses the elements of an OpenURL received from the link 112 and generates links to appropriate resource copies and services based on information concerning the user and the context which is known to the collection owner. The generated links are then typically displayed as indicated schematically by arrow 118 in the user's browser screen display 102 in the form of a link menu 120 containing the links, for example, links 120 and 122. In order to reduce computational overhead, these links are typically not actually resolved until selected by a user. Thus, any given link may be inactive, reach resources that are not accessible or generate multiple results, etc.
Various link resolver servers are commercially available. A link server that is currently popular is the SFX link resolver server sold by Ex-Libris Limited, 313 Washington Street, Suite 308, Newton, Mass. 02458. This server can generate appropriate links from received information in a known fashion.
However, in systems that use the aforementioned link servers, problems can still arise. For example, link servers cannot provide appropriate links in circumstances where the user does not have access to a desired resource. Further, the collection owner may continually acquire and release access rights through purchase and expiration of subscriptions, etc. Therefore, it may be difficult for the collection owner to know at any given time what the most cost-effective copy would be, even given the user and context information.